Featherbeds in use are positioned on top of a conventional mattress. One concern of featherbed construction is to minimize significant shifting (migration) of fill material in the featherbed from one portion of the featherbed to another when the featherbed is in use. When migration is made difficult by a particular construction, however, restoration of the fill to its original location once some migration has occurred is very difficult. Another concern is to provide and maintain a good (high) loft for the featherbed, which provides not only an attractive appearance for the featherbed, but a comfortable, pleasing sensation in use.
Baffles are used in featherbed construction to create loft volumes (chambers) to hold highly compressible material such as feathers and down, and to limit migration of the filling. Baffle box construction is frequently used when baffle walls are higher than two inches. Lateral baffles increase the internal volume, permitting the use of more filling material, which increases initial loft and contouring compressibility. The taller the baffle, the greater the interior volume and the greater the fill weight required. However, the only commercially feasible way to fill the featherbed in manufacture is through openings in the baffles. These openings allow some migration of filling from one baffle chamber to the next in use, which results in the disadvantage of a generally permanent shifting of the filling material, since restoration of filling to its original location after migration is quite difficult with a typical partially open baffle structure.
Baffles have not been completely successful in preventing fill migration and make restoration difficult, if not impossible. Further, baffles produce a featherbed which appears relatively flat to the user, i.e. without significant loft, due to the evenness of the resulting surface of the featherbed, which can in turn give the impression that the featherbed will not provide the desired “sinking-in” sensation so attractive in a good featherbed.
An alternative to baffle construction is “sewn through” construction, in which the top fabric layer of the featherbed is attached directly to the bottom fabric layer, by sewing. An advantage of this construction is that it does control the migration of filling material. The disadvantages include a reduction in the overall loft of the featherbed and compression of the filling material over the entire sleep surface. In addition, the typical sewn-through construction limits the number of internal volumes, allowing contouring and compression because of too much shifting of the fill material within the individual chambers. This creates undesirable pressure points over the surface of the featherbed.
Hence, it is desirable to have a featherbed construction which provides a consistent high loft with an inviting appearance, as well as significant control over the migration of fill, reducing or eliminating uncomfortable pressure points.